Molecular and physiological studies of nitrogen uptake in plants and fungi

在过去的50年中，全球氮肥的使用量已经攀升至每年约1000亿kg，成本约为500亿美元。这些肥料中的大部分从土地上沥滤出来，被冲入河流和海洋，通过微生物的大量繁殖对自然种群造成相当大的环境破坏。它们的快速生长降低了沿海沃茨的氧气水平，例如在墨西哥湾，这定期导致大鱼死亡。在未来几年里，全球人口的增长和农业土地的退化只会加剧这一问题。我的研究重点是调节植物根系氮素吸收的生理和分子机制。营养物质的膜运输是植物生物学的基本组成部分;从环境和经济的角度来看，它也具有相当大的实际重要性。根的硝酸盐吸收是由一个50 kDa的膜蛋白，从真菌到高等植物的生物体共同介导的。我们已经证明这种蛋白质（nrt2.1）需要第二个较小的蛋白质（nrt3.1）的参与。我们已经成功地表达了这两个蛋白在真菌（构巢曲霉），以研究蛋白质相互作用的基础上，使用定点突变。我们将使用荧光显微镜来探索荧光标记的重组nrt2.1和nrt3.1蛋白之间的相互作用和免疫沉淀来验证所提出的二聚体功能单元。与此相关的项目，我们已经表明，真菌硝酸盐转运蛋白的调节posteroptionally，可能是由一个变构机制，涉及蛋白质磷酸化。利用真菌蛋白的定点突变，我们寻求进一步探索这种调节。我们也正在研究拟南芥中的五个根amt 1铵转运蛋白的功能。我们已经通过过表达nrt2.1和nrt3.1在增加烟草干物质产量方面取得了一些初步成功。我们获得的知识可能使我们能够作进一步的改进，这是可能的。我的研究涉及与加拿大，澳大利亚，苏格兰，伊朗和印度的科学家合作，我们定期在UBC接待访问科学家和研究生。

During the last fifty years, global nitrogen fertilizer use has climbed to approximately 100 billion kg per annum at a cost of about 50 billion dollars. Much of this fertilizer is leached from the land and swept into rivers and oceans, where it causes considerable environmental damage to natural populations through blooms of microrganisms. Their rapid growth reduces oxygen levels in coastal waters e.g. in the Gulf of Mexico, where this periodically results in large fish kills. The increasing population growth and degradation of agricultural lands worldwide can only exacerbate this problem in the coming years.My research focusses on the physiological and molecular mechanisms that regulate nitrogen uptake by plant roots. Membrane transport of nutrients is a fundamental part of the biology of plants; it is also of considerable practical importance from an environmental and economic standpoint. Root nitrate uptake is mediated by a 50 kDa membrane protein common to organisms from fungi to higher plants. We have shown this protein (nrt2.1) requires the participation of a second smaller protein (nrt3.1). We have successfully expressed the two proteins in a fungus (Aspergillus nidulans) in order to study the basis of the protein interactions using site-directed mutagenesis. We will use fluorescence microscopy to explore interactions between fluorecently tagged recombinant nrt2.1 and nrt3.1 proteins and immunoprecipitation to verify the proposed dimeric functional unit. Related to this project we have shown that the fungal nitrate transporter is regulated posttranslationally, probably by an allosteric mechanism involving protein phosphorylation. Using site-directed mutagenesis of the fungal protein we seek to further explore this regulation. We are also investigating the functions of the five root amt1 ammonium transporters in Arabidopsis. We have experienced some preliminary success in increasing dry matter yield in tobacco by overexpressing nrt2.1 and nrt3.1. It is feasible that the knowledge we gain may enable us to make further improvements. My research involves collaborations with scientists in Canada, Australia, Scotland, Iran and India and we regularly receive visiting scientists and graduate students at UBC.